The hydroxy analogue of methionine is a well-known chemical compound which is otherwise described as .alpha.-hydroxy-.gamma.-methylmercaptobutyric acid (MHBA). This compound has nutrient values equivalent to the corresponding amino acid, methionine. The calcium salt of MHBA is also well-known, and it is usually in the form that it is used to fortify animal feeds.
Standard methods for preparing the calcium salt of .alpha.-hydroxy-.gamma.-methylmercaptobutyric acid involve reacting an aqueous calcium hydroxide slurry with an aqueous solution of MHBA and ammonium sulfate. After first removing calcium sulfate by filtration, the product calcium salt is recovered from the solution by evaporative crystallization, followed by washing and drying. The evaporative crystallization step is energy-intensive, and this process is becoming increasingly disadvantageous as energy costs rise. Therefore, there is a clear need for a more economical and energy-efficient process for preparing this useful feed supplement.